The embodiments herein relate to in-situ generation of acid for use in subterranean formation operations.
Subterranean wells (e.g., hydrocarbon producing wells) are often stimulated by hydraulic fracturing treatments. In traditional hydraulic fracturing treatments, a viscous treatment fluid is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are formed. While the treatment fluid used to initiate the fracture is generally solids-free, typically, particulate solids, such as graded sand, are suspended in a later portion of the treatment fluid and then deposited into the fractures. These particulate solids, or “proppant particulates,” serve to prop the fracture open (e.g., keep the fracture from fully closing) after the hydraulic pressure is removed. By keeping the fracture from fully closing, the proppant particulates aid in forming conductive paths through which produced fluids, such as hydrocarbons, may flow. As used herein, the term proppant particulates includes “proppant aggregates” defined as coherent body that does not generally become dispersed into smaller bodies without the application of shear.
The degree of success of a fracturing operation depends, at least in part, upon fracture conductivity once the fracturing operation is complete and production is begun. In order to enhance production, in some subterranean treatment operations, traditional fracturing operations may be supplemented with enhanced oil recovery techniques. Such enhanced oil recovery techniques may operate to enhance the conductivity of fractures propped with proppant particulates. One such technique is acidizing a fracture. Acidizing involves injecting an acid (e.g., hydrochloric acid, hydrofluoric acid, and the like) into a portion of a subterranean formation (e.g., into or adjacent to a fraction) in order to create microfractures in the face of the subterranean formation. The acid may create a dendritic-like network of microfractures through which treatment fluids and produced fluids may flow. Another example of an enhanced oil recovery technique is fracture-acidizing, in which an acid is injected into a formation above the formation fracture gradient in order to fracture the formation and simultaneously etch microfractures in the face of the fracture in a non-uniform pattern such that the microfractures remain open after the pressure is removed and the fracture closes.